Recommended LRFD Guidelines for the Seismic Design of Highway Bridges

The ATC/MCEER Joint Venture, a partnership of the Applied Technology Council
(ATC) and MCEER, is pleased to announce the availability of Liquefaction
Study Report, MCEER/ATC 49-1 and Design Examples,
MCEER/ATC 49-2.

The Liquefaction Study Report presents the results
of a study of the effects of liquefaction and associated hazards, lateral
spreading and flow. It is part of a series of reports that comprise these
recommended guidelines.

The study investigated liquefaction hazard implications for the design of
bridges from the perspective of real sites and real structures. The scope
was limited to two sites in relatively high seismic locations, one in Washington
State and the other in Missouri. Actual site profile data and bridge configurations
were used. The study included:

Simplified, conventional liquefaction analyses

Development of both 475-year and 2,475-year acceleration time histories

Nonlinear assessment of the site response to these accelerations, including
the time history of pore water increases

Evaluation of cost impacts of the structural and geotechnical mitigation
strategies

The results for the 475-year and 2,475-year events were compared to assess
the implications of using the larger event for design. Additionally, the conduct
of the study helped synthesize an overall approach for handling liquefaction-induced
movements in the recommended design provisions.

The report includes a CD-ROM containing detailed information for each study
site.

The Design Examples illustrate use of the recommended
LRFD guidelines. The two examples are the eighth and ninth in a series originally
developed for FHWA to illustrate the use of the AASHTO Division 1-A Standard
Specifications for Highway Bridges. The eighth design example was performed
on a five-span continuous cast-in-place concrete box girder bridge and the
ninth design example was performed on a three-span continuous steel girder
bridge. Each example emphasizes different features that must be considered
in the seismic analysis and design process.

Promoting
Seismic Safety: Guidance for Advocates, by Daniel Alesch, Peter May,
Robert Olshansky, William Petak and Kathleen Tierney, is a 200-plus page report
that distills the findings of previous social science and policy research
to provide guidance to seismic safety advocates.

It has two parts. Part 1 is a collection of concise tips for advocates organized
into the following topics: successful seismic safety advocacy, earthquake
basics, ABCs of seismic building codes, policies and legislation, appearing
before committees, informing and persuading, partnerships for seismic safety,
working with experts, effective risk communication, and using the media.

Part 2 is a collection of background papers, developed by the authors, to
support and amplify the advice to advocates in the guidance document.

The report is authored by social science and policy researchers at the three
earthquake engineering research centers, MAE, MCEER and PEER, and was funded
by the Federal Emergency Management Agency.

This combined experimental and analytical study provides
an assessment of the validity and accuracy of analysis methods commonly used
for seismically isolated structures, emphasizing secondary system response,
contemporary seismic isolation systems, and strong and/or near-fault seismic
excitation. A six-story steel model was used in three configurations: flexible
moment-frame, asymmetrically braced-frame and stiff braced-frame. Eight isolation
systems were studied, namely, low damping elastomeric bearings with and without
linear and nonlinear viscous dampers, Friction Pendulum (FP) bearings with
and without linear and nonlinear viscous dampers, low damping elastomeric
bearings with lead cores, and low damping elastomeric bearings in conjunction
with flat sliding bearings. Over 300 experiments were conducted. The various
experimental results were compared with analytical results obtained using
the SAP2000 and 3D-BASIS-ME computer programs. The vast database of experimental
results on secondary system response provided the opportunity to assess the
performance of various seismic isolation systems.

The
study described in this report describes the testing performed to examine
the potential use and behavior of engineered cementitious composite (ECC)
materials in lieu of traditional materials. The materials are proposed for
use in seismic strengthening and retrofit applications. Specifically, an infill
panel system was developed that uses the pseudo-strain hardening properties
of the ECC materials. Laboratory studies examined the effect of different
curing and drying times, the tensile response of different specimen geometries,
and the response of ECC materials to reversed cyclic loadings. The ECC materials
investigated showed a wide range of tensile properties as a function of specimen
geometry and constituent materials. Other key findings are summarized in the
Conclusions section of the report. This study is the first to investigate
the response of the ECC materials to reversed cyclic loadings.

This
report describes an experimental investigation into the seismic behavior and
efficiency of using braced steel infills for steel framed buildings. Cold
formed steel studs (CFSS), typically used in nonstructural partition walls,
were studied to determine if they could be used to laterally restrain braces
against buckling and thus enhance their seismic performance. Four specimens
were designed and cyclically tested: single square tube braces with and without
vertical CFSS and rectangular solid bar X braces with and without CFSS members.
The effects of KL/r ratio, bracing configuration and cross-sectional type
of braces were studied, as well as behavior characteristics of the specimens
with an emphasis on hysteretic energy dissipation. As a result, the CFSS members
showed promise for use in new buildings or as a retrofitting technique in
buildings that lack strength, lateral stiffness and ductility.

Methodologies for Post-Earthquake Building
Damage Detection Using SAR and Optical Remote Sensing: Application to the
August 17, 1999 Marmara, Turkey Earthquake

The study described in this report explores how remote sensing
technology can bring significant benefits to post-earthquake response and
recovery activities, through improved urban damage detection. The Marmara,
Turkey earthquake of August 17, 1999 is used as a testbed, as one of the first
earthquakes where a temporal sequence of Ôbefore' and Ôafter'
optical and radar imagery was available. The authors present a series of qualitative
and quantitative methodological procedures and algorithms, which can be used
to characterize the location, severity and extent of building damage. This
study paves the way for subsequent research, employing very high-resolution
imagery acquired by the new generation of optical satellites. Finally, since
many of the illustrations rely on color to convey meaning, and the report
is printed in black and white, a full-color version is included on a CD-ROM.

In
this study, the authors have developed structural models and numerical techniques
to analyze structures in damage states up to collapse. These are needed to
determine functional limit states required for performance and fragility based
seismic design methodologies. The authors explored alternatives to the widely
used displacement-based incremental iterative algorithms. They developed a
framework, termed a dynamical system, where displacements, internal forces
and other state variables can be treated uniformly. Two methods have been
formulated: State Space and Lagrangian. Both methods clearly distinguish the
modeling of components from the numerical solution. Thus, phenomenological
models of components such as steel connections, reinforced concrete elements,
semi-active devices, shock absorbers, etc. can be incorporated into the analysis
without having to implement element-specific incremental state determination
algorithms.

Proceedings of the Second PRC-US Workshop
on Seismic Analysis and Design of Special Bridges

The
Proceedings are the result of the second in a series of international workshops
on seismic analysis and design of special bridges collaboratively arranged
by MCEER and the State Key Laboratory for Disaster Reduction in Civil Engineering,
Tongji University, Shanghai, China. The workshop themes include seismic design
and retrofit of long span bridges, performance based design, seismic safety
evaluation, soil-pile-structure interaction and pseudo-dynamic and hydrodynamic
experimental study. This volume contains 23 papers addressing a wide range
of these research fields, and includes a summary of research needs and workshop
recommendations. The workshop agenda and list of participants is also included.

The
objective of this research is to provide better knowledge on the seismic behavior
of laced members, which can be broadly applicable to many steel truss bridges
that share similar structural characteristics and details. Commonly encountered
built-up brace details and configurations were collected from actual bridges
that have laced members. Using this information, an experimental program was
conducted to investigate the hysteretic behavior of typical built-up compression
members. Strength capacity of the specimens, obtained from the testing, was
correlated with the predicted strength in the AISC LRFD Specifications. Assessments
of hysteretic properties such as ductility capacity, energy dissipation capacity,
and strength degradation after buckling of the specimen were performed. Nonlinear
pushover analyses were also conducted and correlated with test results. The
observed cyclic inelastic behavior of the specimens showed that these latticed
members can exhibit variable seismic performance and could often fail to meet
the displacement demands for typical braced frames in seismic regions.